The present invention is directed to a method for repairing tissue defects in intervertebral discs, including repair of a spinal joint and repair of fissures in the annulus fibrosus. It more particularly is concerned with repairing the portion of an intervertebral disc that has been subject to damage, such as herniation, resulting from natural degeneration, and/or trauma, as well as to repairing that portion of an intervertebral disc remaining after the performance of a partial discectomy intervention. Such discectomies are conventionally performed to treat a severe hernia of an intervertebral disc.
The term ‘Disc Herniation’ (or ‘disc prolapse’ as they use in Europe) is a broad and general term that includes three specific types of disc lesion, which are classified based on the degree of disc disruption and posterior longitudinal ligament (PLL) disruption. The three main classifications of disc herniation are Protrusion (aka: contained herniation or sub-ligamentous herniation), Extrusion (aka: non-contained herniation, or trans-ligamentous herniation) and Sequestration (aka: free fragment). A disc hernia is a radial rupture of the annulus fibrosus of the intervertebral disc that may be accompanied by a protrusion (sometimes a very large protrusion—also referred to as an Extrusion) of the annulus fibrosus and/or by an extrusion of disc material through the rupture in the annulus fibrosus. The rupture of the annulus fibrosus is often accompanied by a compression of the spinal canal and pressure on the nerve roots that pass through the disc protrusion or extrusion. This usually leads to strong and progressive pain that emanates from the compromised segment of the spine. This condition may require a surgical intervention. Disc Sequestration represents the end-of-the-line for the cycle of disc herniation. This condition manifests when a large ‘fragment’ of nuclear material has detached itself from the main body of the extrusion and is loose in the epidural space. This will typically result in severe compression of the traversing nerve root, the exiting nerve root, and the lateral aspect of the Thecal Sac. Sequestration (aka: sequester, free-fragment) may be excruciatingly painful (back and leg pain—sciatica) and, if centrally located, may occasionally cause the patient to lose control of their bowl and bladder function, i.e., Cauda Equina Syndrome, which is considered a medical emergency.
Patients with a symptomatic disc hernia, and indication for a surgical intervention at the disc, normally undergo a partial or total discectomy operation. In a partial discectomy, protruding annulus disc material and a portion of the nucleus pulposus of the disc are removed. The resulting reduction in the volume of disc material within the epidural space leads to decreased pressure on the compressed nerve roots and/or the spinal cord, respectively. Without repair, the radial rupture defect in the annulus fibrosus will remain and will not close, at least it will not close in a relatively short time. Without repair, a considerable risk of post-discectomy complications, such as a re-herniation of the disc, will remain.
A successful discectomy intervention will result in lasting pain relief for the patient. However, it has been shown that severe post-discectomy complications may occur in about 6-16% of all surgical interventions. These are often caused by events such as a re-herniation of the disc, extensive epidural scar formation or vascularization and nerve ingrowth into the defect in the annulus fibrosus.
The cells of the nucleus pulposus produce cytokines and inflammatory mediators, such as nitric oxide, that have been shown to be responsible for nerve root irritation and sensitization that can lead to severe radicular pain. In a post-discectomy situation, without repair of the annulus fibrosus, nucleus pulposus material may migrate into the epidural space and/or nucleus pulposus-derived cytokines and inflammatory mediators may diffuse into the epidural space through the annulotomy site. Both events may result in post-discectomy complications such as persistent nerve root pain and/or irritation of nocioceptors in the outer ⅓ of the disc annulus.
As a side effect of the volume reduction that is attendant upon a discectomy intervention, the intervertebral disc height, and thus the vertical distance between adjacent vertebral bodies, will be reduced. The decreased intervertebral disc height may be one of the reasons for a re-herniation of the disc. Further, the reduction in intervertebral disc height has been reported to lead to an accelerated mono-segmental degeneration of the annulus fibrosus or of the facet joints of the affected spinal segment.
Research is ongoing with respect to mechanical disc replacements, hydrogel implant replacements and in situ curable polyurethane disc replacements.
Recently, fibrin sealant that included a corticosteroid was used to treat disc problems such as fissures in the annulus fibrosus. In this regard, U.S. Pat. No. 6,468,527 discloses that the composition was injected into a disc (an intra-discal injection) to treat disc problems. In U.S. Pat. No. 6,468,527 the fibrin sealant is injected by inserting an introducer needle into disc, inserting a second needle through the introducer needle that is connected to a dual barrel syringe, and then injecting the fibrinogen and thrombin into the disc. The fibrinogen and thrombin begin mixing at the “Y” connection and throughout the length of the needle.
The inventors herein have identified that a need exists for alternative processes of repairing the spinal joints including the annulus using materials other than fibrin sealant.